Treatment of butane



Patented Aug. 15, 1939 PATENT o Fi fcs murmur F nv'raits .VladimirIpatiefl and 'Herman Pines, Chicago, lll assignors to Universal OilProducts Com pany, Chicago, 111., a corporation of Delaware No Drawing.

Application- September so, 1936, Serial No. 103,390

This invention relates particularly to the treatmentof butan'eof normalor straight-chain structure.

In a more specific sense, the invention is con- ,5 cemed with a. processwhereby normal butane is converted into iso-butane, the processinvolving the use of special catalysts and particular con-i ditionsoioperation which favor the isomerization reactions so that relativelyhigh yields of I!) the iso-compound are produced. v

Since the invention is concerned principally withthe two i-carbon' atomparaiiln hydrocarbons and their transformation, one into the other, thefoliowingtable is introduced to indicate the}.

structure and the principal physical characteristics of these'twocompounds: 1

Butanes are produced in considerable quan titles in the oil refiningindustry. They occur in substantial amounts in natural gases-(in whichthe normal compound usually predominates), in refinery gases 'which areevolved from crude petroleum storage-tanks, and in the primary dis-.tillation oi, crudes, and they are also present inconsiderablepercentages in the gases produced incidental .to cracking heavypetroleum fractions for the production of gasoline. In the case ofcracked gas mixtures the relative proportions of iso and normal butanesvary, but the ratio of the iso to the normal compound is as a ruleconsiderably higher than in natural gas.

Butanes may be considered as moreor' less marginal compounds in respectto their. desirability in ordinary gasoline, that is,'a certainpercentage of them is essential for sufllcient vapor pressure to insureease in starting, while an excess tends to produce vapor lock. For thesereasons the total percentage of 4-carbon atom hy-,

an drocarbons is commonly adjusted in conjunction with the boilingrangeand vapor pressure of the othergasoline components to produce a gasolineof desirable starting characteristics according to seasonal demands. Y r

The butanes at the present time bear a further- "tion is concerned.

important relationship to oil refining inthat their excess production isbeing utilized as a 'source of gasoline either by ordinary'thermaltcracking orby special catalytic dehydrogenation processes iollowed bypolymerizationinwhich 5';

catalystsmay or may not be used. Investigations have shown thatiso-butane is considerably more amenable to cracking and dehydrogenation, I bothwith and without catalysts, than the normal c o m p o u n d. Consideringthe ;-corresponding Inmono-oleflns, the normal butenes areconsiderablymore dimcult to polymerize, either thermally orcatalytically, than iso-butene, and it is foundalso that the 'octenesrepresenting the dimers oi the iso-butene are of higher antiknock valuethan is. 7

those from n-butenes, which'holds; also for the octanes produced byhydrogenation. It is. therelore, of considerable importance at'thepresent time to convert as much as possible of the normal butaneproduction, into iso-butane,.and the present invention is especiallyconcerned with a process for accomplishing this object. r

In one specific embodiment, the present invention comprises treatment ofnormal butane for the isomerization'there'oi into iso-butane, with 25a'catalyst comprising essentially anhydrous aluminum chloride supportedon activated carbon.-

In 'eifecting various reactions'among organic. compounds, utilizingaluminum chloride as a catalyst, difliculty is frequently encountered inthat intermediate addition compounds are formed which are more or lessof a sticky and viscous character, so that the original granules ofanhydrous chlorlde become coated and the effective catalytic surface islost. This tendency may be 35 overcome to some extent by employingvigorous agitation during the course of the catalytic reactions, but itcan never be entirely obviated, so that in general the fulleffectiveness of aluminum chloride is neverattained. These phenomena 40are particularly noticeable in hydrocarbon reactions such as those withwhich the present invenr f Another property oi. anhydrous aluminumchloride which must, be taken into account is its 45 tendency to sublimeat a temperature of approximately C., so that ii itis employed attemperatures above this pointit must be injectedor sublim'e'd into thereaction zone. In the process ofthe present invention, in which thealuminum 60 chloride employed is strongly absi'n'bed by activatedcarbons, both of the disadvantages enumer- 'ated are to a large extentovercome since the tendency of the aluminum chloride to volatilize ispartially counteracted by the absorbent action of the carbons or charsemployed, and these supports further act to absorb and retain some ofthe viscous addition compounds and .prevent the composite catalystgranules from adhering to form large agglomerates.

The method of preparation of the type oi catalyst used for theisomerization of normal butane is to mix a properly activated andadsorbent carbon with anhydrous aluminum chloride and then heat the massunder elevated tempera-e tures and'pressures until the chloride has beenadsorbed into the oi the carbon. The proportions of adsorbent carrierand aluminum chloride maybe varied as desired to make'catalystcomposites of varying activity. It has been found possible and practicalto make stable granular catalysts resistant to disintegrating influencesby using approximately equal parts by weight or. absorbent carbon andanhydrous aluminum chloride. Such proportions, after thoroughmechaniheated at a temperature of approximately 250% C. for severalhours. After such a treatment of the original mix the product obtainedis dry. and granular, the aluminum chloride apparently havingdisappeared, though it is actually present in the pores and on thesurface of the carbon as evidenced by the violent reaction of'thegranules with water and their catalytic activity in organic reactions.

Owing to the adsorptive properties of the ac-.

tivated carbon, catalysts of the above character may be employediniso'merizing normal butane 'wlth substantially no tendency for theoriginal particles to run together due to the formation of intermediatesludge like products, so that much larger quantities of material may betreated before the catalyst has lost its activity. Another advantageresides in the fact that the; adsorbed aluminum chloride will remain inplace without yolatilization-at considerably higher tempera-- lar bed ofcatalyst.

The term activated carbon" as used in the present specification isintended to'include any type of prepared carbon or carbonaceous materialwhich is more or less granular and possessed of good porosity andstructural strength and which has been prepared by general stepsinvolvably under vacuum, to expel adsorbed liquids and 60 gases. It isrecognized that various forms of active granular chars will varyconsiderably in adsorptive capacity so that therefore the proper- "tiesof catalysts prepared in accordance with the present invention will varyboth in respect to the amount of aluminum chloride which they are ableto absorb and in respect to the periods of service in which they areable, to maintain a practical activity in diiferent organic reactions.

We have determined that by the use of the class of catalystsmentioned,and particularly by the concurrent use of considerable superatmosphericpressure, normal butane may be converted into isobutane with ayleld ofas high as 60% to 65%; Evidently the use of superatmosphericpressures ofthe order of 1050 atmospheres at temperatures 01150? c. and higher,besides depressing the volatilization of the aluminum chloride, tendsalso 'to depress numerous undesirable side reactions which would resultin the formation of hydrogen and low molecular weight hydrocarbons,sothat the reaction proceeds more or less in one direction until anequilibrium is established.

The following example is introduced as characteristic of the practicaloperations of the present process, though it is not introduced with theintention of limiting the scope of the invention in exact correspondencewith the numerical data since some latitude is possible in theproportions of activated carbon and aluminum chloride, and

temperature and pressure may also be varied within the limits alreadyspecified. These variations may be considerable in the case of gasmixtures, in which normal butane occurs as a constituent in varyingpercentages.

, In the manufacture oi the catalyst for the isomerization reaction, 100parts by weight of an activated carbon and 100 parts by weight ofanhydrous aluminum chloride were thoroughly mixed in a dry atmosphereand then placed in a pressure vessel lined with glass to avoidcorrosion.

An amount of hydrogen chloride gas was intro-' duced equal to 5% byweight of the total mix and the pressure was then raisedto a totalofatmospheres by the introduction of substantially dry hydrogen. Thevessel was heated to a temperature of 250 C. and the contentsmechanically agitated for a period of three hours. The product had thegeneral appearance of granular carbon but was somewhat more gray thanblack. The particles were entirely homogeneous in appearance and gave avigorous evolution of heat when contacted with water, I

Normal butane conta ning about 2% by weight I of hydrogen chloride waspassed through a granular mass of the catalyst at a temperature of about200 0., a pressure of 650 lbs. per sq. in.

changed n-butane.- Compared-with an equivalent weight of ordinaryannular anhydrous aluminum chloride, the prepared catalyst could be)used approximately four-times as long before the ma.

- ual deposition of carbonaceous :esidues and byaluminum chlorideineiiective. The herein disclosed method oi preparing the catalyst isnot claimed per se in the present ap plication inasmuch as this subjectmatter is claimed in our companion application, Serial No'. 103,391.Theuse of metallic halides broadly, including aluminum chloride, in theisomerlzation of n-butane is claimed in our companion application,serial No. 103,383..

We claim as our invention:

1. A process for producing isobutane which products rendered the action.of the ads rbed comprises subjecting normal butane,- in the substantlalabsence of polymeriza'ble oleflns, to the action' of activated carbonimpregnated with anhydrous aluminum chloride under conditions I suchthat isomerization of normal butane constitutes the principle reactionin the process, wherethe order of about 150 to 250 C., and underpressures of the order of about 10-to 50 atmospheres,

whereby to eflect isomerization of normal butane into isobutane as theprincipal, reaction in the process.

3. A process for producing isobutane which comprises subjecting normalbutane, in the subride under conditions such that isomerization ofnormal butane constitutes the principal reaction in the process, wherebyto convert a major portion of the normal butane into isobutane.

4. A process for producing isobutane which comprises subjecting normalbutane, in the substantial absence of polymerizable oleflns and in thepresence of a relatively small amount of hydrogen chloride, to theaction of activated carbon impregnated with anhydrous aluminum chlorideat temperatures of the order 0! about 150 to 250 C. and under pressuresof the order of about 10 to 50 atmospheres, whereby to effectisomerizationuof normal butane into isobutane as the principalreaction'in the process.

VLADIMIR IPATIEFF. HERMAN PINES.

